System State / An atlas in development
The System Atlas.
One event. Many ways to place it.
Change the map’s reference, follow a world, and look inside a timestamp. Keep the source and the meaning attached. A working first step—not an operational navigation service.
A Gregorian label in TDB. This is not a UTC conversion.
Equal scale on both displayed axes. Body dots are enlarged. This is a geometric map, not a view of arriving starlight.
TRY A CHANGE OF REFERENCE
Keep the state—and its meaning.
Records include source status, body identity, frame, time scale, and limitations. A project also keeps your view and any imported pack.
Same event / different time labels
A timestamp is not a universal clock.
These panels describe the same selected epoch. They do not compare two physical clocks, and they do not impose a day on another world.
01 / SOURCE TIME
TDB is the time argument retained with these astronomical coordinates.
02 / RELATED SCALE
TCB label, related by the IAU’s defined linear transformation. Not a local clock reading.
03 / PROPOSED USST
seconds since JDTCB 2451545.0An explicitly chosen epoch on an established scale. An experimental display convention, not an adopted standard.
Keep the relationship visible.
LB = 1.550519768 × 10−8
T0 = 2443144.5003725
TDB0 = −0.0000655 s
The spatial values stay TDB-compatible. Displaying the related TCB label does not silently rescale positions or relabel their compatibility.
Missing information stays missing.
UTC / your civil clock: not converted in this edition. A UTC label requires the relevant reference data and conversion model. The calendar fields above use Gregorian formatting, but they are labeled TDB or TCB—not UTC.
A clock on a world or spacecraft: unavailable without a trajectory, clock model, and gravitational treatment.
Planetarydians and local calendars: not yet implemented. No surface location or daily schedule is inferred from an orbital period.
System State Day: no synthetic day duration is imposed.
A clear limitation is more useful
than a precise-looking guess.
Data / a reproducible route forward
What is this map made from?
The offline guide and imported ephemerides are different data modes. The source badge stays attached to the map and to every export.
An approximate guide, honestly labeled.
How the real-data route works
The kit contains a Python updater for the Sun and eight planet centers. It requests geometric barycentric ICRF position/velocity vectors in TDB, preserves raw responses, checks identities and headers, and tests interpolation against separately requested off-grid values.
Only after all checks pass does it replace a local data/latest.json file. You can host that file beside the atlas, or open it here manually. No agent and no continuously connected browser are required.
The updater’s live requests could not be completed in this build environment. The package tests its parser and interpolation with explicitly synthetic fixtures; those fixtures are not bundled as real ephemerides.
The boundaries of this edition.
Barycentric Sun motion: enabled only by an imported pack containing a sourced Sun-to-barycenter state. The guide does not estimate it from the visible planets.
Body centers and barycenters: always distinguished. The guide’s Earth entry is the Earth–Moon barycenter, not the Earth’s surface or center.
Imported provenance: metadata is declared by the file. Format checks and checksums do not authenticate NASA or certify physical accuracy.
No extrapolation: an ephemeris pack is usable only inside its time coverage. Outside it, the atlas refuses the date rather than inventing a position.
Privacy: no accounts, automatic saves, tracking, or automatic network requests in this file. “Check hosted data pack” makes one deliberate request to this site’s own data file. Downloads are not encrypted. A hosting site may have separate analytics.
Use: education and prototyping only—not flight navigation, targeting, or safety-critical timing.
Body identities & numerical limitations
Guide errors are JPL’s nominal fit errors, not confidence intervals or certified bounds. Imported interpolation checks describe numerical disagreement at tested epochs, not physical uncertainty.
| Entry | Target / meaning | Source or numerical limitation |
|---|
Primary sources
- JPL approximate planetary positions, Table 1 — coefficients, fitting interval, nominal errors.
- JPL Horizons manual — bodies, frames, vectors, and time scales.
- Horizons API documentation — request and response contract.
- JPL API fair-use policy — sequential requests, caching, and no browser API embedding.
- IAU 2006 Resolution B3 — TCB–TDB definition.
- NAIF SPICE Time documentation — why clock and time-scale conversions need models.
These sources do not endorse USST or this implementation. Documentation checked 23 September 2026.
What has been tested?
The kit includes reproducible numerical, parser, security, and browser tests. Coordinate round trips check internal consistency; they do not validate astronomical accuracy.
In the guide, velocity is the derivative of the changing fitted elements, evaluated using a centered 60-second difference. It is not an observed or Horizons-supplied velocity.
In pack mode, interpolation uses positions and velocities with cubic Hermite polynomials in TDB. The source samples remain unchanged. A record identifies whether its epoch is a sample or an interpolation.
Physical devices, other browser engines, hosting configuration, and a successful live Horizons download need separate checks. The connectivity failure is recorded in the kit.